The present invention relates to a semiconductor device and a manufacturing method of a semiconductor device, and for example, the present invention can be preferably used for a semiconductor device using a nitride semiconductor and a manufacturing method thereof.
A transistor using a GaN-based nitride semiconductor uses two-dimensional electron gas generated at an interface between different nitride semiconductor layers, such as, for example, an AlGaN/GaN interface, as a channel (current path). Therefore, such a transistor realizes high-speed switching characteristics and is expected as a device which can reduce power supply loss and which can be downsized.
Among transistors using a GaN-based nitride semiconductor, in particular, a transistor having normally-off characteristics is useful, so that a structure that causes a transistor to have the normally-off characteristics is studied.
For example, Japanese Unexamined Patent Application Publication No. 2011-29506 discloses a normally-off type semiconductor device having a buffer layer composed of an AlN layer, an undoped GaN layer, an undoped AlGaN layer, a p-type AlGaN layer, and a metal layer composed of Pd or WSi over the p-type AlGaN layer, over a main surface of a substrate comprised of sapphire.